Dental implants consist of metallic, ceramic, or polymeric materials which are placed either on or within the mandibular or maxillary bone to support fixed or removeable prostheses. The function of an implant is to provide an abutment to support and stabilize a prosthesis. Generally an implant is placed in an edentulous area after it is determined that a conventional restorative modality is not satisfactory.
The fundamental problems associated with implant design and application have been: obtaining highly biocompatible materials which withstand the adverse oral environment without corrosion and loss of mechanical properties; designing implant shapes and restorations which provide mechanical support and stabilization for the prosthesis without causing extensive bone resorption; and developing an interlocking between the gingival and mucosal tissues and the implant to retard bacterial penetration and infection in sites where the implant extends into the oral cavity.
Until the so-called Branemark implant, no commercial implant was available for which there was a direct attachment of bone to the surface of the implant via a process called osseointegration. It should be noted that the Branemark implant is a pure titanium implant in which osseointegration can be produced. However, the Branemark implant requires a six month nurturing period. As will be seen, the subject system reduces this healing period to as little as one month by combining osseointegration with osteogenesis or osteointegration, in which new bone is guided directly through the implant.
Note that the implant must be stabilized immediately after placement and must be free of any movement during the healing process. Movement causes formation of a connective tissue interface between bone and implant. This connective tissue provides a flexible cushion and subsequent mobility. Where there is implant mobility, epithelial invagination, and implant failure often occur. As will be seen, the subject system immobilizes the implant during a greatly reduced nurturing period due to its unique pure titanium/captured-bone operation, as well as a new procedure specified for implantation involving multiple high or low speed drilled holes accomplished by water cooling.
More particularly, the main problem with the Branemark implant is that Branemark wishes to obtain osseointegration between the bone and pure titanium. Osseointegration as defined herein means the binding of bone to some foreign material such as pure titanium. While it has been found by Branemark that such osseointegration can in fact occur with pure titanium, the problems are two fold. The first problem is that osseointegration, if it occurs at all, occurs sufficiently only after a six month nurturing period. Secondly, osseointegration may never occur to a sufficient degree to stabilize the implant no matter what time period is utilized.
Other problems include the utilization of any type of sharp edges or screws without any captured bone mechanism for osteointegration which can result in inflammation without subsequent new-bone growth. Moreover, with the utilization of the Branemark equipment there is a problem of the cost of the drilling apparatus which must be slow speed, as well as requiring the exact matching of the drilling diameter to the diameter of the implant, which even if exact, is nonetheless conducive to bone remodelling. Hence, there is a lack of an exact fit because the bone tissue is alive and will react osteoclastically to any kind of surgical procedure.
Note, one of the most important factors with respect to the Branemark or any other implant which utilizes interstices, indents, or other types of orifices, in which bone is to grow is that it is necessary to stimulate bone growth into these interstices, a situation which does not often occur absent the utilization of immobile tightly packed cortical bone within the implant itself which is part of the Subject Invention.
By way of further background, implant systems are illustrated in U.S. Pat. Nos. 3,609,867; 4,277,238; 3,789,029; 3,918,100; 3,790,507; 3,606,615; 4,244,689; 4,131,597; 4,141,864; 4,547,390; 4,595,713; and 4,202,055. In these patents various bone compositions have been utilized to aid artificial bone grafting both in the dental field and in other fields.
One patent in particular, U.S. Pat. No. 4,600,388, indicates an implant with loosely held bone material. One of the problems with the utilization of such loosely held bone material is the movement or migration of the unclamped bone during the healing process which prevents the bonding of bones to the implant. Moreover, any bone-to-implant bonding would occur over dramatically long periods of time or will not occur at all. In other words, loosely-packed particles can prevent bone formation over long distances because of the formation of dense connective tissue surrounding the bone particle.
Additionally, one of the aforementioned patents, U.S. Pat. No. 4,244,689, illustrates an endosseous plastic implant with holes adapted to promote bone growth therein. Note that no bone material is initially placed in the shallow indents and that any bone that grows into the indents is strictly a chance happening which cannot be guaranteed. Moreover, the shallowness of the intercuts does not afford much fixative power. Also because of the dielectric constant of the plastic, no electric charge stimulation occurs to promote bone formation.
Further, in addition to the above-mentioned patents, a pure titanium basket structure made by Friedrichsfeld is utilized for implants in which a relatively large hole is drilled in the mandibular bone, with the basket being utilized to permit bone growth therethrough. However, the basket does not initially carry any bone, such that bone growth is chancy without such positive stimulation. Moreover, the Friedrichsfeld implant can fail because of bacterial ingrowth.
It will be noted that none of the above references cite the utilization of bone which is immobilized or rigidly held in a pure titanium structure, in which the tightly held bone runs completely through the structure to promote ankylosis or bone-to-bone adhesion, blood vessel growth and consequent bone growth guided completely through the implant. It is important in the final stabilization of the implant that the bone growth be promoted completely through the implant and this cannot be accomplished through loose bone particles in a container or merely through the utilization of indents in the surface of an implant or channels therethrough.
As mentioned hereinbefore, for those implants which require drilling, the drills utilized are generally of a diameter equivalent to that of the proposed implant. These drills, aside from being low speed and extremely expensive, do not result in perfect adaption of the implant to the bone on a timely basis unless nurtured for six months, this assuming that the drill hole perfectly matches the implant morphology and that the bone did not react excessively in an osteoclastic manner. If not, then a dense connective tissue capsule forms, preventing bone-to-implant bond or osseointegration.
Most importantly, in all previous implant techniques, the healing process necessary before the implant can be capped with a usable tooth is on the order of six months, a time period in which the patient is deprived of even temporary tooth structure.